Nearly all the time you use the it you will use or need to refer to domain
names.

You will call domains up directly via telnet, Ftp or gopher. On the WWW you
will either call domains explicitly via URL or implicitly via hypertext links.

On email you will mail somebody at a domain:

A typical email address looks like user-name@domain.name.

For example
dave@cs.cf.ac.uk where

dave is my user-name

@ is the standard email separator of name and domain-name

cs.cf.ac.uk is the domain of this department.

URL's are just as easy to read

URL stands for Uniform Resource Locator.

A typical WWW URL is of the form IPtype://domain.name.

For example: http://www.cs.cf.ac.uk

where:

The IPtype is the internet protocol type used for storage and
transmission. On the WWW this is typically Hypertext Transmission Protocol,
http, but can be telnet, ftp, gopher, news (USENET news) or even
mailto (email).

:// is standard URL punctuation to separate IPtype from domain.

Domain name of site some time the domain name you are used to will be
prefixed by www (as in www.cs.cf.ac.uk, www.bbc.co.uk), sometimes the host
is named explicitly.

Following the domain name the directory path and name of file can be
specified. We will see this shortly.